Oxygen tent



M rch 24, 1942. D, J, co' 2,277,072

OXYGEN TENT Filed June 3, 1938 2 Sheets-Sheet 1 March 24, 1942. D. .1. COHN.

OXYGEN TENT Filed June 3, 1 938 2 Sheets-Sheet 2 Patented Mar. 24, 1942 UNITED STATES PATENT OFFICE 2,277,072 OXYGEN TENT David J. Cohn, Chicago, Ill.

Application June 3, 1938, Serial No. 211,540

11 Claims.

My invention relates in general to so-called oxygen tents. It relates more in particular to improved means for maintaining desired atmospheric conditions about a patient, which atmosphere may or may not be enriched with oxygen or other gases.

In many diseased conditions, it becomes necessary or advisable at times to administer to the patient more than the usual amount of oxygen found in the ordinary atmosphere. Because of this requirement, it has been the practice to utilize some type of covering over the bed in the nature of a canopy or tent, and to treat the air within this canopy by suitable means, not only to maintain a relatively high 02 content but also to dehumidify and, where necessary, to reduce the temperature. The canopy so used is commonly referred to as an oxygen tent, and the appellation is extended to include very often the equipment which is associated with the canopy. For convenience, therefore, in the further description of my invention, I shall employ the term oxygen tent according to its popular meaning to include both the canopy and the means for maintaining proper atmosphere therein.

Oxygen tents are continuously coming into greater use, and, except for limitations and disadvantages in designs heretofore used, would have been employed to a much greater extent than they are now. For example, even where oxygen therapy is not required, a suitably functioning oxygen tent can'be employed to advantage in maintaining in contact with the patient an atmosphere of proper humidity and proper temperature for his comfort alone. Oxygen tents heretofore employed, however, had so many disadvantages and inconveniences connected with them that many hospitals preferred to resort to their use only in extreme cases. For example, the cooling medium heretofore employed has been, for the most part, ordinary water ice, usually arranged in chipped form in a compartment at the side of the canopy over the bed, and motor driven fan means was necessary to circulate the air from the canopy through the cooling box and back again into the canopy. Since it is impossible to produce an electric motor which will remain entirely noiseless, this form of device always had associated with it a humming type of noise from the motor, and also blower noises, which most patients found in time to be extremely annoying. The crushed or chipped ice in the ice compartment naturally melts and a great deal of difficulty is had in 55 properly disposing of the water. Moreover, the clinking and dripping associated with the settling of the ice and drainage of the water therefrom are found to be very objectionable by many patients. Others in the room, particularly other patients in plural-bed wards, are distracted by the-type of noise described.

There is also a strong tendency to chill the patient on one side and have uneven temperature conditions generally in the tent when the air conditioning unit is placed at the side of the bed, but it has been impossible successfully to place it directly over the patient because of the relatively large size unit required, the difiiculty of mounting a motor in such position, and of adequately taking care of drainage from the ice compartment, Moreover, the objectionable noises referred to are magnified, particularlyv the clinking and dripping noises occurring when pieces of ice melt and fall.- Attempts have been made to use solidcarbon dioxide in place of water ice, but heretofore without success due in large part apparently to the fact that, because of the extremely low temperature ofdry ice the temperature within the tent or canopy itself would drop too low and problems arose, particularly in connection. with uneven cooling; and also, because of the arrangements attempted, there was excessive leakage of CO2 into the-tent.

Those familiar with oxygen tents and their use are aware that, in addition to the problems and disadvantages discussed above, there are many minor inconveniences, particularly such associated with giving necessary care to the patient, accessibility from both sides of the bed,

and the like. It is perfectly evident to every capable medical man that the provision of an oxygen tent overcoming the disadvantages set out above and manyminor disadvantages and inconveniences which may arise in connection with an individual case will increase tremendously the use of this form of therapy, in many cases only for the purpose of increasing the comfort of the patient.

The principal object of my invention is the provision of an improved oxygen tent.

Another object is to overcome the problems and disadvantages expressed hereinabove as they are known to exist in connection with oxygen tents heretofore designed and employed.

A further object is to produce an oxygen tent which may be employed with substantially no inconvenience to the patient under any circumstances and particularly one which will not have associated with it noises of anykind which; to

the nervous patient and others in the room, might be distracting.

A still further object is the provision of improved means and methods of utilizing dry ice in oxygen tents for maintaining suitable atmospheric conditions.

Further objects are concerned with maintaining a substantially uniform temperature within the tent, the utilization of a smaller unit than heretofore has been possible, the ability to place the atmosphere conditioning unit immediately above the bed to make the patient accessible from all sides, providing for better visibility on the part of the patient, greater cleanliness of the, air conditioning unit and canopy, easy portability, etc.

In general, I overcome thedisadvantages associated with oxygen tents heretofore producedand attain the objects of my invention by th'e utilization of dry ice in a relatively small control unit adapted to be positioned directly over the bed. By providing a relatively great amount of cool surface associated with the dry ice container in contact with the atmosphere and which comprises a part of the control unit, atemperature gradient is established between the atmosphere in the unit of which the dry ice container is a part and the atmosphere of the canopy, so

that fairly rapid thermal circulationis obtained;

thus eliminating, electric motors, their noises, inconvenience and expense. Means is provided for controlling the speed at which the air circulates, and. this control has the effect of increasing or decreasing the temperature by controlling the amount of tent atmosphere coming in contact with the cooling unit. The temperature of the coolingunit itself is controlled by suitable means, conveniently by controlling the surface contact between the dry ice and the inside surface of its container. Oxygen is suitably. introduced so as to diffuse it through the tent atmosphere.

The entire atmosphere conditioning unit, by virtue. of the entire arrangement, is relatively small and light in weight so that it is easily portable and can be set upquickly in an emergency. It is very. easily cleaned and sterilized when required. The canopy itself is. suitably one of the newer, relatively inexpensive, transparent materials, easily shaped up in the form of a canopy for each new patient, and then removed and destroyed after it has been used with that patient. Any other suitabl canopy, however, may be used.

Other features and, objects of my invention will beapparent from a consideration of the following detailed description taken with the accompanying drawings, wh'ere in Fig. 1 is a. perspective view showing one embodiment of my invention in. positionv to be applied over the bed of a patient;

Fig. 2 isa. side-elevational view illustratingone position which the unit may havewith respect to the patients bed;

Fig. 3 is an enlarged transverse sectional" view showing features of the dry ice container and preferred means for introducing oxygen;

Fig. 7 is a fragmentary sectional view, partly in elevation, illustrating a modification of the arrangement of the dry ice container; and

Fig. 8 is a similar view illustrating a still further modification.

Referring now to Figs. 1 to 6, inclusive, of the drawings, the oxygen tent as a whole comprises a control unit indicated generally by the reference character l0, and a canopy generally indicated by the reference character I The canopy is adapted to be placed over a patient I2 reclining in a usual hospital bed. The unit In is supported by a suitable stand [4 adapted to be placed next to the bed so as to carry the unit substantially directly over the patient.

In the embodiment shown, the unit in comprises a single side frame member l5 and end members I! and I8. These members are preferably formed of relatively light weight sheet metal welded or brazed together to be air-tight, and covered with a suitable insulation I!) such as sheet cork or the like. This material has the advantage of being relatively light in weight, provides adequate insulation and a nice finished appearance. Other insulating materials may, however, be employed, such as materials which will stand a sufficiently high temperatur to permit direct heat or steam sterilization of the entire unit. This structur comprises a shell or box through which the air circulates and within which oxygen is preferabl introduced, as will be shown. Sealed within th'e outer partition is a cooling unit comprising generally a tubular dry ice container 2|, this container being somewhat longer than the distance between the end members I! and I 8, and the end members being shaped to seal the container to provide a gas-tight enclosure.

One suitable manner of sealing the container 2| within the end members of the shell is illustrated in section in Fig. 6. In this form, the end member I8 has an annular projecting flange 22 just slightly larger than the contiguous end portion of the tubular container so that an annular insulating and packing member 23 is disposed between them. A cup-shaped end member 24 is provided, telescoping over the annular flange 22. A circular sealing and insulating member 26 is fitted within the end of the cylindrical container 2|, and a generally similar member 21, but of somewhat greater diameter, is disposed between the end of the annular flange 22 and against the end of the tubular member 2|. A layer of insulation 28 extends entirely over the outside of the cup-shaped member 24. A port 29 extends through th cup-shaped member 24 and its insulation and also through the circular packing and insulating member 21, terminating, however, at the packing and insulating member 26. A ringshaped sealing member 3| is interposed between the inside surface of the end member l8 and one of a plurality of fins or vanes 32, the principal function of which will be referred to hereinafter.

The result of this construction is to obtain a seal between the end of the cylindrical container 2| and the end member comprising a part of the outer shell or box, so that no carbon dioxide will be able to seep from the container into the atmosphere circulating on the outside thereof. In experimental work, I have found that, even though an end plate be soldered or brazed on the cylindrical container 2 there is a marked tendency for carbon dioxide to seep through. With the present construction, seepage is substantially prevented. However, should there be any seepage at the end of the cylindrical container, the carbon dioxide seeping through will escape through the port 29 as a vent rather than move backwardly along the outside of the cylindrical container.

The other end of the cylindrical container 2| also projects beyond the opposite side wall 21 and is fitted with a generally cup-shaped cover 33 having insulation 34 on the outside thereof, and a fiat, circular insulating and sealing member 36.

on the inside thereof. While this cover may be fitted directly over the end of the-cylindrical container, sealed suitably within the shell or box within which it is contained, I preferably utilize a construction generally similar to that described in connection with the other end thereof. The end member I1 is provided with an annular, upwardly projecting flange 31 and an annular packing and insulating member 38 is disposed between this flange and the end portion of th container. The cover fits over this outwardly projecting flange. A ring-like sealing member 39 is disposed between the inside face or surface of the end member H and one of the fins 32. The cover is provided with a suitable handle, as shown, and a nipple 4| sealed through the cover is adapted to receive a hose 42, through which means the carbon dioxide, after sublimation in the form of a gas, may be withdrawn from the container 2|. At the cover end, as in the opposite end, the construction is such as by calculation to prevent escape of carbon dioxide at the sealed end of the container, but, should there be a tendency for the carbon dioxide to escape because of some small leak, the carbon dioxide will escape to the outside rather than into the interior of the shell or box through which the tent atmosphere circulates.

The fins 32 previously referred to are suitably secured in direct contact with the outside surface of the cylindrical carbon dioxide container. A suitable method, such as shown, is to provide an annular, generally right-angular flange which lies fiat against the outside surfac of the cylindrical container, and connection is made, by welding, brazing or the like, to produce a substantially integral structure. Preferably I finish the fins and the outside of the cylindrical container in a dark color to facilitate heat transfer from the circulating tent atmosphere to the dry ice container and the fins forming a part thereof.

Within the container 2|, I provide a support 43 for dry ice 44. This supportis formed of suitable insulating material capable of producing a fair amount of insulation and alsopreferably formed so as to retain its shape. Its principal function is as a temperature control, and, to suit it to this purpose, suitable means, such as a handle mechanism 45, is provided for permitting moving it circumferentially of th inside of the container 2|, for example to the two positions indicated in Figs. 4 and 5 and such intermediate positions as may be desired depending upon conditions sought to be maintained within the canopy covering the patient. Since the, cylindrical container 2| is formed of metal and, therefore, possesses a relatively high degree of heat conductivity, and the support member 43 is formed of an insulating material and, therefore, has much less heat conducting capacity, the relative amount of heat that will be extracted from the atmosphere moving in contact with the fins will depend upon the proportion of dry ice in direct contact with the metal of the container as compared to the proportion which is in contact only with the insulating support member 43. There is an atmosphere of gaseous CO2 in contact with the entire inside wall of the container and this atmosphere will, of course, be relatively cool. It by no means, however, has a cooling effect equivalent to that of the dry ice or solid carbon dioxide; indeed, the gas may itself act as an insulating material, as will be pointed out hereinafter in another connection. The principal cooling effect is through the direct contact of the dry ice itself with the wall of the container. In Fig. 6, the insulating support member 43 is supporting the dry ice substantially entirely out of contact with the side walls of the container and so the cooling effect will not be as great as when the support member 43 is in the positin indicated in Fig. 4. By further contrast, in the position indicated in Fig. 5, the insulating support member 43 is not supporting the dry ice at all, and a cooler atmosphere will be obtained when the'c'ontrol is in this position than when it is in the position illustrated in Fig. 4. The support member 43, therefore, by virtue of its adjustability, functions as a temperature control, working independently of other temperatur controls which may be employed and which will be described hereinbelow.

Solid carbon dioxide or dry ice may be obtained in various forms. Preferably I utilize it in the form of a solid having a maximum transverse dimension not substantially less than the diameter of the container 2|. A square cross section is suitable, utilizing a shape which would be defined geometrically as a right-angular parallelepiped. I have found that pieces 3% inches square by 10 inches long are suitable and can just be accommodated in a cylinder constructed of a suitable size to give ample cooling and adequate atmosphere circulation. When the oxygen tent is to be used for an adult, the cylindrical container 2| is made long enough to accommodate two of such pieces of dry ice disposed end to end, and for children the container may be made shorter to receive only one such ten-inch piece, while for infants still less dry iceis needed, a block of smaller cross section being preferred. These figures are only illustrative and are given for complete guidance of those skilled in the art and not as limiting the scope of the invention. It is clear, also, that the particular shape of the dry ice is not of prime importance so far as functioning of the oxygen tent is concerned, but is mostly a matter of convenience and simplicity. Since the dry ice sublimes at the'surface, utilization of the same general surface area, such as results when a standard form is utilized, simplifies the matter of accurate control in the use of the oxygen tent of my invention. 7

In addition to controlling the temperature of the container 2| and fins 32, I provide additional controls concerned with predetermining the amount of circulation obtained when the temperature conditions are constant. There is also the feature of maintaining the direction of circulation constant when the oxygen tent is moved to one side of the patient or the other, the matter of defrosting and other features. Apparatus associated with the shell or box H! is utilized alone or in combination with other features for accomplishing the purposes suggested, and this apparatus will now be described.

A lower central member 46, conveniently of concavo-convex shape and preferably comprising a section of a cylinder, is provided with hinge members 41 which are pivoted at the outside of end members l1 and I8. This permits the member 46 to be dropped to the general position indicated in dotted lines in Fig. 3, or to be moved upwardly to the position shown in full lines in this figure. A latch member 50is provided ateach end of the. unpiyote'd side to hold it in its upper position, whichis the normal position during operation. End members, generally arcuate on both sides, form a part of the lower baflie member 46 and lie outsidethe end members I! and I8, and it is against the end membersthat the latches U engage to hold this member in position. These end members also result in forming a dish-like upper cavity in the concavo-convex member for catching condensate, as will be described hereinafter. Themember 46 is formed to combine adequate strength, cleanliness and insulating characteristics by employing a suitable construction, such as laminations of sheet metal and sheets of insulating material. A suitable construction is to utilize a sheet of insulating material entirely covered with sheet metal. Other similar constructions, however, may be used.

Positioned below the container 2| above the member 46, and disposed between the two end members I1 and I8. of the outer shell are a pair of spaced baflles 48 and 49. These battles are positioned generally so as to define an acute angle, although generally tangent to a circle slightly larger than defined by the fins 32 A suitable position which gives very good results is shown in Fig. 3. Like the member 46, the baflies 48 should combine suitable strength, insulating characteristics and the property of being easily kept clean. A suitable construction is produced by employing rectangular sheets of insulating material entirely covered with sheet metal. These bafiles 48 and 49 have their ends suitably secured, by welding, brazing, or the like, to the metal portion of the end members l1 and I8. Spaced from the upper ends of the bafiles 48 and 49 are hollow support members 5| and 52. These members are formed to receive a flat support rod 53, carried by the stand l4 for supporting the entire oxygen tent. They also have pivoted to them louvers or vanes 54 and 56, these louvers or vanes extending the full length between the end members I! and I8 and being adapted to engage against the outside upper edge of the bafiles 48 and 49, respectively, to substantially entirely seal the space between the side walls l6 of the shell and the baffles 48 and 49. The lower end of the battles 48 and 49 carry louvers or vanes 51 and 58. from end to end of the shell, and are adapted to close the space between the bottom edge of the baflies 48 and 49 and lower baffle member 46. The louvers 54, 56, 51 and 58 are so hinged as to remain in any position to which they can be adjusted without other support than'their hinges. They are formed of suitable material, preferably metal, coated with a relatively thin layer of insulating material.

Each of the end members I! and I8 is formed at the bottom with an end or trough as indicated at 59 in Fig. 3. Each of these troughs is provided with a lip 6i forming a spout whereby to empty aqueous contents, of the trough into the dish-like upper portion of the concavo-convex baflie member 46. Sealed through the member 46 is a tube 62-into which a narrower tube 63, secured to and emptying into a trap 64, isadapted to extend. A short tube 66 is sealed through the bottom of the trap 64 and is adapted to have secured thereto a flexible discharge tube 61 which may suitably be stoppered by a spring clamp as shown. The tube 63 has its lower terminus inside the trap 64 at a point below the top of tube 66 and, therefore,

.50 These louvers or vanes also extend below the level ofany liquidcontained in the trap. The tube 62 'is sealed'throughthe material of the canopy l I, so that the trap is outside of the tent and, therefore, will not interfere with the patient in any way.

Oxygen may be introduced into the tent. atmosphere in any. suitable manner when employing the principles of my invention, although I utilize preferably the arrangement illustrated in Fig. 6. A pipe 68, provided with a plurality of perforations69, is sealed through the end member I! and at its end to the inside surface of vend member 11. Thus, the. oxygen is admitted only through the apertures or ports. 69 which are distributed uniformlyalong the length of the pipe 68. A flexible connection H, such as a suitable flexible tube, has one end attached at the projecting end of pipe 68, and the other end adapted to be connected to a suitable source of oxygen, for example, a usual type of drum containing oxygen under pressure and equipped with the usual regulatory apparatus.

The canopy ll maybe suspendeddirectly from the unit I0. However, in order to provide a somewhat greater space below the canopy, I provide an extension support 12 which may satisfactorily comprise a relatively heavy wire bent to shape and having its ends inserted in suitable sockets provided at the sides of unit l0.

While the canopy may be formed of any suitable material for preventing admission of room atmosphere to the patient, I prefer to utilize some of the more recently developed, relatively inexpensive, imperforate, transparent materials such as some of the rubber derivatives now known to the trade. The rubber derivatives known now on the market, such as the one sold under the trade name of Pliofilm, are illustrative of the materialwhich I may employ. Employing, such materials, a canopy is simply and inexpensively formed from flat sheets secured together by adhesive tape material, such as the tape conventionally known to the trade as Scotch Tape. The same type of tape may be employedto attach the canopy to the control unit I0, using the general form of support indicated at '13 at the right hand side of Fig. 3, or as illustrated also in Fig. 6. The canopy is formed so as to give the patient as much freedom as possible, but also to permit the lower edge of the canopy to be inserted suitably under the mattress and covers so as to make a substantially effective seal at the bottom.

While any suitable type of stand l4 may be utilized, I find considerable advantage to flow from the use of a stand of the general type illustrated in Figs. 1 and 2. In this form, an upright 14 is carried at one side of the base, and a second upright 16 telescopes within the upright 14. Brackets are carried on the two uprights and a simple form of screw arrangement is disposed between the two brackets to control the relative positions of the uprights l4 and I6 and hence the height of the unit [8 above the bed. The adjusting mechanism between the mutually telescoping uprights 'l4 'and 16 comprises brackets 10 carried by the uprights in the lower of which an adjusting screw 15 is swiveled, the said screw being threaded in the upper bracket. Thus turning the adjusting screw positions the height of the unit H] by fixing the relative positions of the mutually telescoping uprights. The adjusting screw also has the function of holding the uprights in their adjusted position. An enclosure from which the adjusting screw projects carries the brackets and telescoping portion of the uprights thereby preventing the possibility of injury should a patient accidentally place his hand on the mechanism during an adjusting operation. Since the upright is at one side of the base, the base is suitably positioned beneath the bed with the upright along side of the bed, and, since the weight is suspended out over the bed, the center of mass is maintained over the center of support and there will be little or no tendency for the oxygen tent to be upset even though an extremely flexible and manipulative system is maintained at all times. In other words, the oxygen tent may be placed in. position on a few minutes notice or may be shifted from one side of the bed to the other with very little inconvenience, but, when in position, it is supported firmly.

While the functions of most of the apparatus described will, in general, be clear from the preceding description, these functions will be understood with somewhat greater clarity by a consideration of preferred methods for using the oxygen tent of my invention, particularly from the standpoint of the functions and advantages flowing from its use.

Let us assume that the parts are in the position shown in full lines in Fig. 3 and that the patient occupies the same general position in this figure as illustrated in Fig. 2. Before the tent has been placed over the patient or coincident therewith, the cover of the container 2| is removed and a suitable quantity of dry ice, substantially enough to fill the container, is introduced and the cover placed back into position. This causes the outside of the container and the fins 32 to be reduced to a very low temperature with the result that the air in contact therewith is cooled and the cool atmospheredrops by gravity to a position just above the lower baffle member 46. At the same time, the warm atmosphere about the patient moves upwardly following the general direction of the upwardly pointing arrows in Fig. 2 so as to enter between the baflle 48 and the open louver 54. As this circulation starts, the louver 56, being closed, and the louver 58 open, the cold atmosphere will pass across the face of louver 58 and generally outwardly and downwardly following the general path indicated by the arrows. In so moving, this cold atmosphere will be mingled with other atmosphere under the canopy so that, by the time it reaches the patient, it will have entrained a certain amount of warmer atmosphere with it and also partly have become dissipated by being mingled with the other atmosphere and atmosphere of just the right temperature will move across in contact with the patients head and face.

Moisture is present in the breath exhaled by the patient, but, since this exhalation occurs in the position shown, this portion of the warm air containing the greater proportion of themoisturev from the patients body moves upwardly and into contact with the fins and outer surface of the container. Because of the low temperature, the moisture is removed from this atmosphere and accumulates in the form of ice very gradually on the surface. By this means, the relative humidity is kept between and 50% which has been determined as desirable in most cases. At the same time that the circulation starts, oxygen in suitable amounts may be introduced through the ports or apertures 69, and the oxygen so introduced is distributed uniformly in the remaining atmosphere as it passes around the container.

The patient gives off carbon dioxide in his breath and while normally it might be expected that this carbon dioxide would accumulate, I have found that, when the arrangement which I show is employed, the continuous admission of oxygen is sufficient to permit enough leakage of tent atmosphere around the bottom of the canopy so that the CO2 content of the tent atmosphere will notbe raised above the amount known to be proper in a given case. There seems to be considerable diffusion of CO2 as well through the material of the canopy. If desired, however, any suitable CO2 absorber may be used, as those skilled in the art will understand.

If the unit is to be supported on the opposite side of the bed than that assumed, the disposition of the louvers or vanes would be just the-opposite, and the same circulating properties would be retained, that is to say, the louvers 54 and 58 would be closed andthe louvers 56 and 5'! opened, and the air path with respect tothe patient would still be relatively the same as indicated by the arrows in Fig. 2. Should it be desired to utilize a control unit which would be supportable only at one side of the bed, or at the back of the bed, such a unit may be formed to provide circulation in only one direction, that is to say, it would be provided with only two openings, one for admis-.

sion of warm air near the patients head and another for the emission of cooler air to produce the cycle described. Particularly in the case of relatively small oxygen tents to be used for infants or very small children, and which, therefore, may be made very small, exceptionally good results are obtained by mounting the oxygen tent on a stand supported at the head of the bed, and such a small unit need be equipped with only adequate controls for maintaining suitable temperature conditions. It may be noted at this time that, while I prefer to produce the movement cycle indicated in dotted lines in the drawings, that is, with the cold atmosphere moving downwardly away from the patients face, then upwardly across the face, and the warm exhaled gases moving substantially directly upwardly, the atmosphere may be moved in other ways, for example across the bed laterally, while still employing some of the features of my invention. I may however, is not particularly desirable in most cases because it is apt to produce such unequal distribution of cold and warm atmosphere within the tent as to chill the patient in spots. This has been the disadvantage in oxygen tents-in which the movement of tent gases was across the patient laterally, the result being in many of these cases to chill one shoulder and arm of the patient, usually to his great discomfort.

For controlling the temperature of the atmosphere within the tent, I may employ several means, as has been generally suggested hereinabove. Initially, the temperature of the fins and container 2| which comprise the cooling unit may be controlled by suitable manipulation of the member 43 or by modifying the quantity of dry ice within the container. The temperature may also be controlled by adjusting the position of the louvers, since unrestricted passageways allow the maximum circulation, and restricting the passagewaysby partly closing the louvers cuts down the circulation and, therefore, reduces the temperature. I find that I may also modify the temperature by controlling the rate at which the dry ice sublimes in the container 2|. For example, by partly closing off the hose connection 42, less vaporous carbon dioxide is permitted to escape, and this not only decreases somewhat the rate of sublimation by changing the Vapor pressure characteristics between the solid dry ice and the gas surrounding it, but it also forms a blanket or layer of warmer gas in contact with the inside wall of the container which, in itself, acts as an insulator. Conversely, for extremely rapid cooling, suction could be placed on. the hose line 42, although such extreme measure is not warranted if the unit is adequately designed to take care of extreme conditions. The radial position of the nippleor tube 4| is also of some importance as a control feature.

Since the cooling material which I employ, namely dry ice, sublimes directly, it avoids the disadvantages inherent in the use of water ice of requiring some means for taking care of drainage. It has another advantage in that it more adequately removes moisture from the atmosphere of the tent as the moisture is-given off by the patient, and holds that moisture in the form of ice for a long period of time without any tendency toward dripping which would be disagreeable from the patients standpoint. I find that usually the moisture can be allowed to collect on the fins for a period of approximately twelve hours before defrosting is necessary. As a consequence, the drain jar shown in the drawings is normally not required to be kept in position, but may be placed out of the way during approximately thetwelve-hour period referred to. For defrosting, all that is necessary is to leave the cooling unit empty for a short interval, and the relatively small amount of ice which has accumulated will quickly melt and run oiT quietly through the trap which is provided with the water seal. During defrosting, water resulting from the melting of all of the accumulated ice flows into the upper portion of the concave portion of the baffle member 46. During this period, such water as may tend to drip directly onto the baifles 48 and 49 is obviously directed into the dishportion of member 46, and such very small amounts of moisture as may collect during the defrosting or at any time along the inner walls of the outer shell will be delivered through the trough provided at the bottom and escape at the lips 6| into the member 46. Because the outer wall is relatively warm as compared to the fins, there is very little tendency for much condensation on these inner walls. In this connection, it will be noted also that only a relatively small amount of outside insulation is required because the inner surfaces of the outer shell are constantly being swept with relatively warmer atmosphere and this acts as an insulation between the relatively very cool fins and the outer shell.

While in general, in the operation of an oxygen tent, it is preferable to maintain a relatively low CO2 content in the tent atmosphere, and a relatively high 02 content, there are times when the patients condition indicates the use of an atmosphere relatively high in carbon dioxide. Under such conditions, I may, by suitable control means, deliver such proportion of the carbon dioxide escaping through the tube 42 as may-be necessary to maintain the tent atmosphere as high in CO2 value as desired. This added carbon dioxide may be introduced directly under the canopy, or it may,.by suitable means, be introthorou'ghly with the remaining portion of the tent atmosphere as it circulates in contact with the fins. .This avoids the use of separate CO2 drums which are sometimes required with oxygen tents of the prior art;

In the modifiedform of the invention shown in Fig. '7, I illustrate only one end of the container 2|, sufiicient to illustrate one means for permitting the complete removal of the dry ice container where such provision may be deemed advisable. In this form, an aperture 8| is provided in the end member generally circular and having sufficient area to pass the fins 32. A removable closure member 82 is provided, and means such as bolts and thumb nuts, as shown, is provided between the end member I1 and the closure member 82 for attaching the closure member in position to close the opening 8|. At the point of engagement between the closure member and the container 2|, suitable sealing provision is provided, in the form shown an annular flange 83 on the closure member 82, and a cooperating annular flange 84 integrally secured to the outside surface of the container 2|. If desired, as an alternative structure, the annular flange 83 may be secured directly to the container 2|, but the provision shown allows for-the use of only a single closure member 82 capable of ducedwithin the control unit so that it will mix employment with a plurality of removable containers. In this form, the cover may be generally of the same structure as that shown in the first described embodiment.

The other end of the container 2| may be formed exactly as illustrated in Fig. 6, the end of the cylindrical portion sliding into the position there illustrated, and the pressure exerted by the closure member 82 being sufiicient to provide for adequate sealing.

An advantage of this form is that no defrosting is required while the oxygen tent is in position over the patient. At the end of the period when defrosting normally would be required, it is necessary only to remove the container and supply a fresh container filled with its complement of dry ice, thereby continuing the regular circulation and making it possible to defrost the removed container in a service room without inconvenience to the patient.

In the form shown in Fig. 8, the same general construction is provided as shown in the previous embodiment except that the container 2| is given a sliding fit in the end members of the outer shell, and isprovided with an outer flange 86 fitted with handles 81. Through this construction, the container 2| may be rotated a partial revolution, the handles 81 serving to facilitate rotation, and also indicating the position of the container at any time. Because of the circulation ofthe tent atmosphere, one portion of the container will accumulate most of the moisture, and, by then rotating the container topresent a fresh portion into the path of the atmosphere at that point Where the moisture is removed continued operation may be obtained for a longer period of time without defrosting. Properly controlled, several adjustments may be made Without accumulating sufficient frost on the container to prevent satisfactory operation.

It is obvious that either'or both of the embodiments shown in Figs. 7 and 8 may be employed with the features shown in the first described embodiment. So far as the operation and functioning of the oxygen tent as a whole is concerned,

it will not be affected in any way, and so the description of the operation of the first-described embodiment can be taken as a description of the operation of the embodiments of Figs. 7 and 8, except for the changes obvious from the nature of such embodiments.

Whatever embodiment may be employed, my invention makes possible utilization of a much smaller and more efiicient oxygen tent than has been considered possible heretofore. While my invention contemplates the use of dry ice only, it is clear that some of the features of my invention may be employed with other refrigerants than dry ice with suitable advantage. Where also I describe the special means for controlling temperature, it should be borne in mind that control of the tent temperature is almost automatic once the oxygen tent is placed in position and adjusted. The dry ice sublimes more rapidly or more slowly depending upon the heat given oil by the patient. For this reason, it is possible to produce a unit designed in accordance with my invention without adjustable louvers, and provided with only openings of such a size that the normal patient, in anormal room atmosphere, will remain comfortable due to this self-regulatory feature described.

Because of the small size, compactness and light weight of my oxygen tent, it is very suitable for use outside a hospital. By the employment of a suitable collapsible stand, the entire apparatus required may be housed in one or two convenient hand carrying cases, which may be kept in the usual out patient department of a hospital and, instead of requiring hospitalization where oxygen therapy is required, the apparatus may be quickly delivered to the home and set up over the patient just as conveniently as if he were in the hospital. It may stand for long periods without servicing, which is a characteristic very desirable for home use. i

I have described my invention in detail for the guidance of those skilled in the art, but it is obvious that various changes and embodiments may be made within the general scope of my invention as defined in the appended claims.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. In an oxygen tent of the character described, a control unit adapted to be supported substantially directly above a patient, said unit comprising an outer shell having a single side member and end members, the side member open at the bottom and formed so as to permit relatively free circulation of tent atmosphere in contact with its inner surface, a dry ice container sealed against the end members but spaced from the side member of the shell to form a generally annular circulation space around said shell having two passageways interconnecting the same with that space in the oxygen tent above the patient, said two passageways being substantially as long as said dry ice container, and means including louvers associated with said shell for promoting circulation of tent atmosphere between the said container and the outer shell, the construction and arrangement of said louvers being such that said louvers may be adjusted to adjust eifectively the height of said passageways with respect to each other and the cross sectional area of either or both of said passageways whereby tent atmosphere may be caused to circulate around said dry ice container in either direction and whereby, due to the cross sectional area of either or both of said passageways, the rate of said circulation may be controlled.

2. An oxygen tent as defined in claim 1, wherein said last-mentioned means comprises a passageway between the shell and container, and another passageway disposed substantially below the container, both of said passageways running transversely across the patient, and provided with means to control their cross sectional area, said first-mentioned passageway disposed substantially directly above the patients head, and the second-mentioned passageway having a louver positioned to direct cold atmosphere downwardly and toward a position in front of the patient, whereby warm air in contact with the patient will tend to move directly upwardly, and cool air from the unit will tend to be mixed with portions.

of the tent atmosphere in front of the patient whereby the atmosphere coming into direct contact with the patient is of substantially moderate temperature and above the, temperature of the.

atmosphere delivered from the unit.

3. In an oxygen tent of the character described, a control unit adapted to be placed substantially directly above the patient, said control unit comprising an outer shell having a generally arcuate shaped side member and end members connected thereto, a container for dry ice or the like of generally cylindrical shape sealed in the end members and spaced from the generally arcuate side member to permit circulation therebetween, a pair of b-afiles connected between the side members and disposed in the general form of aV below the said container, a concavo-convex member disposed below lower edges of said bafiles, whereby relatively long passageways are provided between upper edges of said baifies and the arcuate side members and between lower edges of said bafiles and said concavo-convex member, and adjustable louvers adapted to close or open said passageways.

4. The combination defined in claim 3, including means for s p g said unit from either side of a bed, said louvers adapted to be adjusted for causing circulation of tent atmosphere between said shell and said container whereby to prevent cold atmosphere from the control unit from coming into such direct contact with the patient as to cause local chilling.

5. The combination defined in claim 3, including means for delivering all aqueous liquid during defrosting into said concavo-convex member, and means for delivering the said aqueous liquid from said concavo-convex member to a position outside ofthe tent.

6. In an oxygen tent of the character described, an outer shell member having an arcuate side member and end members, said shell member adapted to have a canopy attached thereto to extend over a patient, said shell member being closed except for a lower opening substantially co-extensive with that portion thereof within the canopy, a dry ice container sealed against the end walls of said shell, but spaced from the arcuate side wall, whereby to provide a generally annular space between the end members of the shell, the atmosphere of which is adapted to be chilled below the temperature of the tent atmosphere around the patient, and whereby the chilled air will tend to move downwardly into the space enclosed by the canopy, means providing passageways of different elevation connected to said annular space, whereby to cause circulation of tent atmosphere therethrough, and means for controlling the speed at which such air transfer takes place, and the direction of movement of the air during such transfer, whereby oxygen may be introduced within the canopy, and continuously recirculated over said dry ice container to pre ventloss of oxygen and maintain comfortable atmospheric conditions within the tent.

7. In an oxygen tent of the character described, an outer shell member having an arcuate side member and end members, said shell member adapted to have a canopy attached thereto to extend over a patient, said shell member being closed except for a lower opening substantially co-extensive with that portion thereof within the canopy, a dry ice container sealed against the end walls of said shell, but spaced from the arcuate side wall, whereby to provide a generally annular space between the end members of the shell, the atmosphere of which is adapted to be chilled below the temperature of the tent atmosphere around the patient, and whereby the chilled air will tend to move downwardly into the space enclosed by the canopy, and means for controlling the speed at which such air transfer takes place, and the direction of movement of the air during such transfer, whereby oxygen may be introduced within the canopy, and continuously recirculated over said dry ice container to prevent loss of oxygen and maintain comfortable atmospheric conditions within the tent, said last mentioned means comprising an arcuate member and two bafiie members disposed below the dry ice container, the arcuate member below the ballles, whereby toprovide four longitudinal passageways, two between the battles and the inside shell wall, and two between said arcuate member and said baflles, and adjustable louvers in said passageways to close or open any selected one or group of them.

8. In an oxygen tent of the character described, a control-unit adapted to be placed substantially directly above the patient, said control unit comprising an outer shell having a generally arcuate shaped side member and end members connected thereto, a container for dry ice or the like of generally cylindrical shape sealed in the end members and spaced from the generally arcuate side member to provide a circulation passage therebetween, a pair of bafiies connected between the side members and disposed in the general form of an upright V below the said container and below said circulation passage, a centrally disposed lower member having its upper surface concave disposed below lower edges of said baffles, whereby relatively long passageways are provided between upper edges of said baflles and the arcuate side members and between lower edges of said baffles and said centrally disposed lower member, said relatively long passageways connecting with said circulation passages between the dry bination a temperature control unit, means for supporting the unit directly over a patient, and a canopy suspended from the unit and insertable around a patient to provide a closed space in which a suitable tent atmosphere may be maintained, said control unit comprising a generally cylindrical container for dry ice, and a shell surrounding the container, the parts being so constructed and arranged that a generally annular circulation space is provided between the shell and container, means providing an intake passageway communicating with the said annular space, and substantially coextensive in length with the dry ice container, and means forming a discharge passageway spaced from the intake passageway and below it, whereby tent atmosphere will enter said intake passageway, pass through said annular space in contact with the dry ice. container, and be discharged at the discharge passageway.

10. In an oxygen tent of the character described, a control unit adapted to be supported directly above a patient, cooling means including a cylindrical container for dry ice forming a part of said control unit, and means other than circulation of air around said dry ice container for controlling the temperature of said cooling unit when a given quantity of dry ice is disposed within the container, said last-mentioned means comprising an insulating support within the container covering a portion of the interior surface thereof, and adapted to be moved radially to cause said dry ice to contact more or less of the surface of the container, the cooling effect of the dry ice being determined by the relative proportion thereof in contact with said insulating support as compared to the proportion thereof in contact with the inner wall of the container.

11. An oxygen tent assembly, comprising in combination a temperature control unit, means for supporting the unit directly over a patient, and a canopy suspended from the unit and insertable around a patient to provide a closed space in which a suitable tent atmosphere may be maintained, said control unit comprising a container for dry ice, and a shell surrounding the container, the parts of the shell and container being so constructed and arranged that a generally annular circulation space is provided between the said container and shell substantially coextensive with the latter, means providing an intake passageway communicating with the said annular space and of substantially the same length as said annular circulation space, and means forming a discharge passageway spaced from the intake passageway and below it, whereby tent atmosphere will enter said intake pass-ageway, pass through said annular space in contact with the dry ice container, and be discharged at the discharge passageway.

DAVID J. COHN. 

